High temperature, oil saving, rapid cook fryer system

ABSTRACT

A deep fat fryer able to quickly cook food items, in about one-third to one-half of a typical cook time in the art for corresponding food items, includes a high powered, preferably high efficiency heating unit utilized to establish a cooking oil temperature in the order of about forty or more degrees Fahrenheit above a typical cook time, while preferably remaining lower than or equal to 410° F. A controller regulates the heat input from the heating unit so as to keep the temperature of the oil from dropping drastically after a product to be fried is placed in the oil for cooking. The amount of cooking oil employed is minimized. A sensing arrangement is utilized to input sensed operating conditions to the controller in order to maintain a desired operating temperature and oil level.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention pertains to the art of cooking and, moreparticularly, to an oil-based fryer system designed for use in a highheat input rate, a high temperature range, with a minimal amount of oil,to perform rapid cooking operations.

2. Discussion of the Prior Art

Oil-based frying is commonly used as a cooking method for a wide rangeof food. Of particular interest to the present invention is the use offryers in fast food restaurants to cook various food items. Compared topreparing drinks and assembling burgers and sandwiches, frying is a timeconsuming process. The cooking of french fries is of particular concerndue to their associated short holding times. More specifically, it isgenerally desired to limit the time, between cooking of the fries andthe selling thereof, to be in the order of seven to ten minutes. Iflonger holding times are permitted, customer dissatisfaction can ensuedue to poor product quality which, in turn, can negatively affect thebusiness and its reputation. Due to these time constraints, it is oftennecessary to cook new fries to order, which typically takes from 2½ to 4minutes, plus time for salting, bagging and serving. As a result, theserving of french fries represents the most common source of customerwaiting time delays in fast food restaurants.

To address these concerns, a typical fast food restaurant may have up tothree fryers in place to minimize delays, particularly during peakbusiness hours. During off-peak hours, the same number of fryers wouldobviously not be needed. Of course, whenever the fryers are on, adegrading of the oil occurs, sometimes without a correspondingproduction of a commercially viable product. In general, the quality ofthe oil in a deep fat fryer will inherently degrade continuously overtime, eventually reaching a level that affects the quality of theproduct in an unacceptable manner. The general practice in the foodservice industry is therefore to dispose of vats of oil used for deepfat frying on a regular basis, ranging from daily to weekly. Oil cost isin fact one of the largest components of the total operating expense forfried products. Of course, a certain amount of that cost is unavoidableas the oil becomes part of the product being sold, generally in theorder of 15% of the final product weight.

When cooking french fries, there are two major processes taking place.In the center of the french fry, the potato is cooked in a mannersimilar to boiling, with raw potato flavors being stripped out by steam.Steam is generated in the core itself and leaves the french fry throughpores in the potato. Physical chemistry dictates that the temperature ofthe core cannot rise above about 212° F. On the other hand, moisture atthe outer surface of the french fry will have evaporated to dry out thepotato, so the temperature can approach that of the oil itself. At thesetemperatures, typically at approximately 300°–350° F., the potato isessentially being toasted and the characteristics that distinguishfrench fries from boiled potatoes are produced. Toasting is primarily achemical process which rapidly accelerates as temperature increases.

Although increasing the temperature of the oil is known to reduce thenecessary frying time, known fryers have a practical upper limit. Thatis, at some point, toasting would occur so fast that the outer surfaceof the potato would bum before the raw potato flavors can be strippedfrom the core. In addition, use of any higher temperatures wouldinherently speed up the degradation of the cooking oil which limits theuseful lifetime of the oil in the fryer. Because of oil degradation, andthe economics of disposal, frying is rarely done above 375° F. Forfrench fries, cooking oil is typically kept at 350° F. or less.

In addition, during the course of cooking a batch of french fries, thetemperature of the cooking oil will dip down as much as 50° F. Becauseof this drop, a graph of oil temperature versus time over such a cookingoperation is often referred to as a “U-curve” (see enclosed FIG. 6). Theprecipitous drop in temperature is a result of melting and/or vaporizingthe large quantity of free moisture present in the original frenchfries. Actually, more than three-quarters of the total energy requiredto cook fries is consumed by vaporizing/melting, with approximately halfof this energy being expended in essentially the first 10–15 seconds ofthe cooking operation. This oil temperature drop does not stop untilvaporization is balanced or exceeded by heat arrival to the fries, whichdepends on a combination of heat input to the fryer and dispersion ofthe heat throughout the oil. When the temperature drop of this U-curveis considered, it can be seen that the amount of cooking timeimprovement that can be achieved through raising oil temperature incurrent fryers is small.

Attempts have been made in the prior art to reduce cook times in fryers,as well as to extend the useful life of the oil. To this end, it hasbeen proposed in the art to provide a recirculation system for a fryerwherein the oil can be continuously or periodically filtered. At thesame time, slightly elevated operating temperatures of the oil can beachieved. However, regardless of these attempted improvements, thetechnology utilized in connection with commercial fryer arrangements,particularly those found in fast food restaurants, have not changed forquite a lengthy period of time. More specifically, cook times generallyin the order of, say three minutes for typical ¼″ shoestring frenchfries are still employed almost invariably throughout the industry.Therefore, there still exists a need in the art for an improvedoil-based fryer system which can significantly reduce the associatedcook time, while reducing or eliminating oil disposal, therebyrepresenting significant efficiency and cost effective advantages in theindustry. In addition, such a rapid cooking fryer arrangement shouldminimize the actual number of fryers needed to produce a given output,thereby reducing not only initial expenditures for machinery, but alsorepresenting cost savings associated with reduced spacing needed for themachines.

SUMMARY OF THE INVENTION

The present invention is directed to a deep fat fryer which is able toquickly cook food items in about one-third to one-half of a typical cooktime in the art for corresponding food items. In accordance with theinvention, a high powered, preferably high efficiency heating unit isutilized to establish a cooking oil temperature in the order of aboutforty or more degrees Fahrenheit above a typical cook temperature, whilepreferably remaining lower than 410° F. In the most preferred form ofthe invention, a direct fired, high powered, high efficiency infraredgas burner is utilized. A controller regulates the heat input from theheating unit so as to keep the temperature of the oil from droppingdrastically after a product to be fried is placed in the oil forcooking. The amount of cooking oil employed is minimized to onlyslightly more than enough to cover the product, e.g., preferably between⅛″ and ½″ above the product. Most preferably, the volume of cooking oilat the cooking temperature is in the order of 3.0 to 4.75 times thevolume of the food items. A sensing arrangement is utilized to inputsensed operating conditions to the controller for use in connection withregulating the heating unit. In addition, low oil level conditions aredetermined, such as by a sensor or calculating arrangement, in order tomaintain a desired oil level by balancing the amount of new oil addedversus the amount of oil inherently withdrawn from the vat with theproduct being cooked.

With this arrangement, the total amount of time needed to cook frenchfries or other food items is brought down to the same magnitude of timeas the preparation of a sandwich and drink order. The rapid cookingarrangement also reduces the amount of oil transferred to the product.This results in reduced oil cost and a healthier food product.Therefore, the invention represents a significant advantage to both therestauranteur and the consumer. In any event, additional objects,features and advantages of the present invention will become more fullyapparent from the following detailed description of a preferredembodiment thereof when taken in conjunction with the drawings whereinlike reference numerals refer to corresponding parts in the severalviews.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a rapid cook fryer system constructed inaccordance with the present invention;

FIG. 2 is an exploded view of the main components of the fryer system ofFIG. 1;

FIG. 3 is a detailed view of a fry pot incorporated in the fryer systemof FIG. 1;

FIG. 4 is a perspective view of a portion of the fryer system of FIG. 1,particularly depicting a heater arrangement utilized in accordance witha preferred embodiment of the invention;

FIG. 5 is a block diagram of an overall control arrangement for thefryer system; and

FIG. 6 is a graph comparing a known oil temperature curve with that ofthe fryer system of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

With initial reference to FIGS. 1 and 2, a deep fryer constructed inaccordance with the present invention is generally indicated at 2. Fryer2 is shown to include a housing or cabinet shell 6 that is adapted to besupported upon a floor through a plurality of legs 10. Housing 6 definesa recessed cavity 15, as well as a rear platform 20. At a front portionof housing 6 is mounted a control panel 28, as well as a pivotable door35 having an associated handle 37. Fryer 2 also includes a vat 42 which,as will be described more fully below, is adapted to be selectivelypositioned within recessed cavity 15. Fryer 2 also includes a basket 46having a handle 47. Finally, a container 50, adapted to house a supplyof replenishing oil for vat 42, is removably mounted upon rear platform20.

Particular reference will now be made to FIGS. 1, 2 and 4 in describingadditional details particularly associated with housing 6. As shown,housing 6 preferably includes an upper peripheral ledge 60 that extendsabout recessed cavity 15. Recessed cavity 15 itself has upper and lowerside wall portions 64 and 65, with at least upper side wall portion 64being defined by a heat shielding insulation and lower side wallpositions 65 being provided with various exhaust openings 66. At abottom of recessed cavity 15 is provided a heating unit which isgenerally indicated at 70. In accordance with the most preferred form ofthe invention, heating unit or heater 70 is constituted by an infraredgas burner having electronic ignition and variable heat output as willbe discussed more fully below. Exhaust openings 66 are provided at lowerside wall portion 65, above heating unit 70, for exhausting gases which,preferably, are directed out housing 6 below and behind platform 20.

As perhaps best shown in FIGS. 1–3, vat 42 includes a plurality of walls82 having associated outside surfaces 84. Although not shown, in themost preferred form of the invention, outside surfaces 84 would beblackened for heat transfer purposes. Vat 42 also includes a peripheralrim 88 that extends outwardly from walls 82 and which is adapted to restupon upper peripheral ledge 60 of housing 6 when vat 42 is insertedwithin recessed cavity 15, with bottom 90 of vat 42 also being blackenedand spaced above heating unit 70. Vat 42 is also shown to include anupper extension 92 which projects above peripheral rim 88. An interior96 of vat 42 is adapted to contain a cooking medium, particularlycooking oil. Preferably, an oil level indicator strip 105 is mounted onone of walls 82 in order to enable a quick visual reference of the levelof the oil.

Also extending into interior 96 of vat 42 is a first sensor 110. Inaccordance with the most preferred form of the invention, sensor 110constitutes a thermocouple having a tip 111 which projects aconsiderable distance below upper extension 92 and a terminal plug 112arranged remote from interior 96. As shown, a second sensor 118 ispositioned against one of walls 82. Second sensor 118 is also preferablyconstituted by a thermocouple that includes a tip portion 119 in contactwith bottom 90 and a terminal plug 120 which extends away from interior96. In the most preferred form of the invention, a respective wall 82 ofvat 42 is provided with an elongated indentation 128 within which tipportion 119 of second sensor 118 extends. A bracket 134 includes a firstportion 136 that is secured to vat 42 for the use of a mechanicalfastener 137, and a curved portion 138. First portion 136 of bracket 134preferably projects across second sensor 118, while curved portion 138extends about first sensor 110. In this fashion, bracket 134 securesfirst and second sensors 110 and 118 in a desired position. Inaccordance with this embodiment, first sensor 110 is adapted to beutilized in sensing the temperature of cooking oil placed within vat 42,while second sensor 118 is utilized to sense a temperature of vat 42directly at bottom 90. The manner in which the sensed signals areutilized in connection with the overall operation of fryer 2 will bedetailed below.

In general, basket 46 is constructed in a manner widely known in the artso as to include a wire mesh body 146. As shown, control panel 28includes a main power switch 154 which can be used to turn fryer 2 on oroff. Even with main power switch 154 turned to the “ON” or “COOK”position, the operation of a cooking sequence with fryer 2 is preferablyinitiated through the use of a start switch 156. In general, the startswitch 156 takes the form of a button. Preferably, start switch 156would be activated before or simultaneously with the placing of basket46 in fryer 2 or the cooking sequence of fryer 2 could be automaticallycontrolled, such as based on a sensed, rapid temperature drop in theoil. Control panel 28 includes a first indicator 160, which ispreferably linked to main power switch 154 in order to provide anilluminated signal concerning the activation condition of fryer 2. Asecond indicator 161 constitutes a light which becomes illuminated upondepressing of start switch 156. Shown centrally along control panel 28is a time indicator 162, which preferably takes the form of amulti-digit LED or LCD display.

Finally, of the main components of fryer 2, resupply container 50 isshown to include a lid 176 and a spout 180. As indicated above,container 50 is adapted to be supported upon rear platform 20 of housing6. In this position, spout 180 extends below platform 20 so as to beabove recessed cavity 15 as clearly shown in FIG. 1. At platform 20,housing 6 is provided with a pair of electrical connectors 186 and 187which are used to activate an electronic valve, generically indicated inFIG. 5 at 190 arranged within container 50 in order to selectivelydispense oil from spout 180 in a manner which will be described morefully below. Although also not shown, container 50 can incorporate aninternal heater for liquefying a cooking medium as needed. Also shown aspart of housing 6 adjacent platform 20 is a pair of sockets 197 and 198which are adapted to receive plugs 112 and 120 respectively.

In general, fryer 2 is utilized by positioning vat 42 within recesscavity 15, with plugs 112 and 120 being simultaneously inserted withinsockets 197 and 198 respectively. Vat 42 is supplied with a cooking oilwhich, in the preferred embodiment, represents a relatively small amountcompared to fryers used throughout fast food restaurants today.Specifically, vat 42 is preferably sized to receive in the range of 6–9pounds of a cooking medium. In general, basket 46 is commensurate insize with those currently found in the marketplace, however, vat 42 ismade much smaller so as to more closely conform to the overall body 146of basket 46. Container 50 is mounted upon rear platform 20 while beingaligned with electrical connectors 186 and 187. Further details of theoperation and synergistic results achieved through the use of fryer 2will now be described with particular reference to FIGS. 5 and 6.

As indicated above, the present invention defines a fryer system 2having a greatly reduced cook time compared to prior known arrangements,while further representing significant oil saving costs. In connectionwith the operation of fryer 2, a CPU 210 is interconnected through apower supply 213 which is preferably represented by a standard ACelectrical outlet. With main switch 154 positioned in the “COOK”position, CPU 210 can control heating unit 70 to heat the cooking oilprovided within vat 42. The temperature of the cooking oil is relayed toCPU 210 through thermocouple 110. In order to provide the reduced cooktime, the temperature of the cooking oil in accordance with the presentinvention is provided in the range of 380°–410° F. Most preferably, thetemperature range is between 390°–410° F. Once this temperature isreached, as relayed to the user through indicator 161, french fries orother food items placed within basket 46 can be lowered into vat 42.With the depression of start switch 156, a timer 164 will resetindicator or display 162 and begin a countdown of the cook time.

Based on the operation of fryer 2 in connection with cooking anexemplary pound of french fries, as will become more fully evidentbelow, the french fries are adapted to be cooked in less than or equalto 70 seconds and, most preferably, about 60 seconds. In other words,the cook times are generally less than or equal to ⅓ to ½ of a customarycook time found in this art.

Because of the initial high temperature differential between the frenchfries and the cooking oil, the energy source defined by heating unit 70,which has a variable heat input rate, is initially controlled throughCPU 210 to increase the heat input to the food items. In accordance withthe example of cooking french fries, this initial cooking stage providesa heat input to the french fries of greater than 50,000 Btu/hr/lb. Mostpreferably, the heat input during this initial cooking stage is greaterthan or equal to 75,000 Btu/hr/lb. In general, during the initialcooking stage, 40–60% of the total energy needed for cooking is impartedto the product. Of the overall cooking time, this initial cooking stagegenerally constitutes about a quarter of the time and, most preferably,less than or equal to 15 seconds. Based on this initial controlling ofheating unit 70, even though there is a rather larger temperaturedifferential between the french fries and the cooking oil, thetemperature of the cooking medium is maintained within the desiredrange.

After the initial cooking stage, the heating rate for the cooking mediumis reduced while maintaining the desired temperature. Again, this iscontrolled through CPU 210 based on signals received from at leastsensor 110. Additional signals received from sensor 118 assures bottom90 does not overheat, while potentially enabling a more accurate controlof heating unit 70 by anticipating necessary heat input changes based onthe temperature of vat 42. Since heating unit 70 preferably extendsalong substantially the entire bottom 90 of vat 42, a relatively uniformheating of the cooking medium occurs. Additionally, natural and forced(bubble) convection aids in establishing uniform heating. As indicatedabove, the byproducts of combustion are drawn through natural and atleast partially forced convection from between heating unit 70 andbottom 90, through exhaust outlets 66 and cabinet 6 preferably adjacentplatform 20, and exiting at the upper back portion of housing 6. Withthis arrangement, the exhaust gases will also function to preheat theoil in container 50, preferably to about 200°–250° F. An induction fan(not shown) or exhaust recirculation could be employed to enhance oilheating. In any event, as clearly shown in FIG. 6, an ideal temperaturerange is maintained by controller 210. The oil temperature is preferablymaintained below 410° F., preferably between 390° and 410° F., to avoidrapid oil degradation, as well as to protect against scorching andimparting off-flavors to the product, particularly based on the oillevel utilized in accordance with the invention.

During the cooking operation, the food items will inherently soak up acertain amount of the cooking oil. Given the low amount of cooking oilutilized in accordance with the invention, a significant fraction ofthis cooking oil could be soaked up. For example, in the case of frenchfries, in the order to 15% of the final product weight can berepresented by cooking oil which has been soaked into the product.Utilizing the low amount of oil in connection with the invention assuresa relatively high turnover rate in that the average age of the oil invat 42 is relatively low. That is, the oil gets carried out in theproduct before the oil has any appreciable time to degrade to anunacceptable level. However, it is necessary to assure that the oil isreplenished. Although this could be performed manually, it is preferablein accordance with the present invention to automatically orperiodically refill vat 42 by the oil in container 50. Therefore, CPU210 functions to signal resupply valve 190 to cause a pre-establishedamount of oil to be introduced into vat 42. In any event, this level canbe regulated in various ways, such as based on the number of cookingoperations or through a direct sensing arrangement. If too low of an oillevel is present in either vat 42 or even container 50, such as throughsensor 110 and/or sensor 118, an alarm (not shown) can sound. Inaddition, or in the alternative, activation of fryer 2 through startswitch 156 can be prevented by controller 210. Regardless, given therelatively high turnover of oil, the need to dispose of oil is reducedor completely eliminated in accordance with the present invention whichtherefore results in a huge savings for the restaurant owner. However,since the operating conditions of fryer 2 specify a fast cookingoperation, the amount of oil transferred to the product is somewhatreduced which further minimizes oil costs and reflects appreciably onthe quality of the food product.

With the control of heating unit 70, the “U-curve” associated with priorknown arrangements is greatly reduced and an extremely uniform overallcooking arrangement is established. Although the presence of a smallamount of cooking oil has a potential disadvantage in that the oilcannot act as a thermal storage for energy, thermal storage is notnecessary in accordance with the present invention due to the ability ofheating unit 70 to provide high input rates. Although, as indicatedabove, heating unit 70 is preferably constituted by an infrared gasburner arrangement, other types of high temperature and high efficiencyheating arrangements could be readily employed. However, with the lowamount of cooking oil, the surface area to volume ratio is high suchthat the oil temperature can rise at a rapid rate. Having less oil alsomeans that the heat input is physically closer to the food product suchthat the heat arrives faster. Finally, in a small quantity of oil, theturbulence caused by bubbles at the surface of the frying material cancarry over to the walls 82 of vat 42, thereby greatly increasing theheat transfer coefficient at walls 82 relative to that of naturalconvection.

Although described with respect to a preferred embodiment of theinvention, additional changes and/or modifications could be made to theinvention without departing from the spirit thereof. For instance, amechanism can be employed to automatically lower basket 46 upondepressing start button 156 and to raise basket 46 when the elapsed timeis complete. Given that a few seconds could result in a significantamount of additional cooking, this automated operation, preferablyperformed through controller 210, may be desirable. In the alternative,or in addition to the above, an audible alarm is provided in a mannercommon in the art. In addition, a periodic or continuous filtering orcleansing system for the cooking oil can be employed. As indicatedabove, the reduced amount of oil utilized in accordance with thisinvention greatly minimizes or eliminates the need for such a filteringsystem, but it may be desirable to remove burnt comestibles from withinthe vat 42. With respect to oil replenishment, it should be noted thatdeep fat fryer systems employed in certain restaurants pump fresh andused oil to respective storage tanks that are refilled/emptied byservice personnel. It should be readily recognized that deep fryer 2 ofthe present invention could be hooked up to remote storage tanks throughsuitable hoses in a similar manner.

Again, although the preferred embodiment of the present invention hasbeen disclosed with particular reference to the cooking of french fries,it should be recognized that various food products can be cooked in deepfryer 2. Obviously, the cook time, oil temperature, vat oil quantity andheat input rate could vary depending upon the particular food productbeing cooked. In accordance with the present invention, it can begenerically stated that the cook time employed with deep fryer 2 is inthe order of about ⅓ to ½ of a typical cook time found in the industry.With respect to oil temperature, the higher temperature employed isabout 40 or more degrees Fahrenheit above a conventional oiltemperature, but preferably always less than or equal to 410° F. Withrespect to the quantity of oil in vat 42, only enough oil to cover theproduct being cooked plus a small amount more, such as in the order of⅛″ to ½″ above the product, is employed. Preferably, the volume of oilat the cooking temperature should be in the order of 3.0 to 4.75 timesthe volume of food product. It should be noted that this refers to theactual volume of the food product, i.e., without air spaces. Inaddition, this volume relationship is based on the oil being heated, asthe oil expands when heated. In any event, this is considerably lessthan conventional fryer systems wherein food products are typicallysubmerged well below an upper oil level in a cooking vat. Related to theminimal quantity of oil is that the width of vat 42 is such that basket46 just fits therein with a minimal amount of clearance, while alsobeing arranged directly adjacent bottom 90. Finally, with respect to therequired heat input, the rate is controlled to greatly reduce oreliminate the U-curve as discussed above, while enabling oil temperaturerecovery to occur in the preferred 15 second period. In general, theheat input rate can be estimated by dropping a basket of product intothe fryer vat at a desired initial temperature with the burner turnedoff, followed by measuring the oil temperature over time. The percentageof the total temperature drop that occurs after 15 seconds is thenmultiplied by a theoretical amount of energy required to cook a pound ofthe product in order to arrive at the required energy input. Thetheoretical energy is calculated from knowledge of the amount of waterloss from the product during the cooking process, the initial producttemperature and the estimated final water vapor temperature and heatcapacity of the dry product. Again, all of these parameters have beenspecifically identified with respect to a preferred embodiment of theinvention in connection with cooking french fries, but the invention iscertainly not limited for use with this particular food product.Instead, the invention is only intended to be limited by the scope ofthe following claims.

1. A system for frying food items, the system comprising: a vat forholding and heating cooking oil; an energy source able to provide heatto the vat by automatically selecting one of at least three inputheating rates; and a controller for receiving signals indicative of atemperature of the oil and the vat and providing an output signal to theenergy source.
 2. The system according to claim 1, further comprising acontainer for providing non-recycled oil to the vat.
 3. The systemaccording to claim 1, further comprising: a first sensor for detecting atemperature of the oil cooking in the vat; and a second sensor fordetecting a temperature of the vat.
 4. The system according to claim 2,wherein the container further comprises an electronic valve responsiveto a signal from the controller.
 5. The system according to claim 1,further comprising: a housing including a recessed cavity within whichthe vat is situated, said recessed cavity being provided with heatshielding insulation.
 6. The system according to claim 1, wherein theenergy source constitutes an infrared gas burner.
 7. The systemaccording to claim 6, wherein the vat includes a bottom wall, saidinfrared burner being positioned beneath the bottom wall and extendingsubstantially an entire extent of the bottom wall.
 8. A system forfrying food items, the system comprising: a vat for holding and heatingcooking oil; an energy source for providing heat to the vat in at leastthree input heating rates; a controller for receiving signals indicativeof a temperature of the oil and the vat and providing an output signalto the energy source; and a container for fresh oil mounted above thevat, the container further comprising a control valve responsive to thecontroller.
 9. The system of claim 8, further comprising sensorsoperably connected to the vat and the controller for providingtemperature signals.
 10. The system of claim 8, wherein the vat is sizedto hold about 6–9 lbs of cooking oil.
 11. The system of claim 8, furthercomprising a cooking basket about the size of the vat.